Method and means for particle and light wave interaction

ABSTRACT

Method and means for creating an interaction between a beam of particles and electromagnetic waves, particularly at optical frequencies, wherein a high velocity beam of particles, such as electrons, is passed through a suitable interaction zone, for example, in the form of an optically transparent dielectric target, such as a thin crystalline film, while the target is irradiated with laser light polarized generally in the direction of travel of the particles, whereby the particles upon striking a suitable medium, such as a non-luminescent screen, give off light of the same color as the laser, which becomes visible on the screen. The interaction thus derived can be used in many particular applications such as, for example, in a color television tube and other electronic display or information storage devices.

455-609 AU 233 EX FIP8106 XR 3,730,979

a ML 1 a, United States Patent 1 y in] 3,730,979 i Schwarz et al. 7 451May 1, 1973 [54] METHOD AND MEANS FOR PARTICLE W. Clark, Gerald W.Grifiin, Henry T. Burke, Thomas AND LIGHT WAVE INTERACTION F. Moran,Howard .1. Churchill, R. Bradlee Boal, [76] Inventors: Helmut J.Schwarz, 49 arver Cir- Chnstopher Dunham and Thomas Dowd cle, Simsbury,CQHIL; Heinrich W. P Hora, Rotdomweg 4, 8012 Ot- [57] ABSTRACT tobrunnBie Munich, Germany Method and means for creating an interaction 5 [22]Filed: 7 1970, between a beam of particles and electromagnetic waves,particularly at optical frequencies, wherein a [2]] N04 high velocitybeam of particles, such as electrons, is

315/3, 4 cles upon striking a suitable medium, such as a non-luminescentscreen, give off light of the same color as References Cited the laser,which becomes visible on the screen. The in- UNITED STATES PATENTSteraction thus derived can be used in many particular applications suchas, for example, in a color television 3,267,383 8/1966 Lohmann ..3 15/3tube and other electronic display or information 3,231,779 H1966 White.l 1 5/4 storage devices.

Primary Examiner-Robert I... Griffin 25 Claims, 4 ng Figu es AssistantExaminer-George G. Stellar Attorney-Robert S. Dunham, P. E. Henninger,Lester move MECHANISM l7 sczssnme DIAPHRAGM 20 /0 li LASER Hz a I ICOOLING svsrem TARZET 3 52% TARGET i summer I? I I A 5/ ELECTROU lELECTRON 501mm SORPIIO GUN BEAM PUMP PUMP Fo c u sms J L |cs i 2, 5 a" lW, passed through a suitable interaction zone, for exam- 52 us. Cl..l78/5.4 R, 315/4, 331/945 A, p in the form of an Optically transparentdielectric 350/ 147 target, such as a thin crystalline film, while thetarget [51] Int. Cl ..H04n 9/22 is irradiated with laser light polarizedgenerally in the [58] Field of Search ..250/ 199; 350/l60 R; directionof travel of the particles, whereby the parti- Patented May 1, 1973 4 I3,130,979

4 Sheets-Sheet 1 BELL SCREEN JAR q MOVEMENT MECHANISM "7 SCREENINGPOCKELS' DIAPHRAGM It l V illlllllfi 10 Ii 'I E I LASER L #BEAM opncs IM: II coou-e I? 5Y5TEM 4 TARZET- v TARGET S PPO T /2 U R ION F 5 I PUMPV ELECTRON I L v ELECTRON soap'non SORPTIOU GUN 55AM PUMP PUMP FOCUSHUGi l L I OPTICS J 3 4 7 2s INVENTORS HELMUI' J. SCHWARZ BY HEM/RICH w.HOAA.

' ATTORA/EY BACKGROUND OF THE INVENTION The present invention relatesgenerally to the field of electromagnetic wave interaction and moreparticularly to a method and means for producing an interaction betweena beam of particles and electromagnetic waves, particularly at opticalfrequencies.

The use of various electronic devices to produce an interaction betweenelectromagnetic waves in the lower frequency portion of theelectromagnetic spectrum is long-established and well known in the artand is widely applied in such fields as AM, FM and televisionbroadcasting and various radar and microwave applications. Also, theinteraction of high frequency electromagnetic waves and particle waveshas been observed, such as in the diffraction of x-rays by a crystallattice, the lattice being regarded as a standing particle wave.However, although P. L. Kapitza and P.A.M. Dirac suggested as early as1933 in the Proceedings of the Cambridge Philosophical Society, that,conversely, high frequency electromagnetic waves should act as adiffraction grid for a particle wave, it was not until 1965 afterdevelopment of the laser, that such an interaction was experimentallyobserved and reported by Schwarz et al. in PHYSICS LETTERS 19,202 (1965)wherein an electron beam was diffracted by a standing electromagneticwave. This further confirmation of particle-wave duality led theinventors to the consideration of whether particle waves, such as anelectron beam, might also be interacted with traveling elecv tromagneticwaves, such as a laser beam, to achieve momentum transfer.

This interaction was a heretofore unobserved phenomenon. Utilizing themethod and means of the present invention, such as interaction between aparticle wave and a traveling electromagnetic wave has been achieved,thus permitting the application of this phenomenon to a vast number ofelectronic and optical devices.

SUMMARY OF THE INVENTION The present invention involves a method andmeans for interacting a beam of particles with electromagnetic waves,particularly at optical frequencies, and essentially comprises thepassing of a high velocity beam of particles through a suitableinteraction zone, such as an optically transparent dielectric target inthe form of a thin crystal, while irradiating the target with a beam ofelectromagnetic radiation, which is preferably coherent, that is, alaser beam, and whose electrical vector is polarized generally in thedirection of propagation of the particle beam. If the particle beamafter interacting with the laser beam is then permitted to fall on anon-luminescent medium such as an alumina screen, light of the samewavelength as that of the laser beam will be given off and becomevisible on the screen. This interaction phenomenon is apparently broughtabout by the presence in the interaction zone of an appropriate targetmaterial which lowers the speed of light in the zone allowing momentumtransfer among the particles, the radiation and the material, as will bemore fully described.

The interaction may be applied in a wide range of electrical devices,such as in the areas of broadcasting,

communications, information storage, data processing and the like andmay be particularly embodied, for example, in a color television tube,or similar display apparatus, as will be described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammaticrepresentation of a system for interacting a high velocity electron beamwith electromagnetic radiation at optical frequencies in accordance withthe present invention;

FIG. 2 is a plot obtained with the system of FIG. 1 representing therelative intensity (I/ o) Of blue light 4480A) given off at thenon-luminescent screen as a function of the distance r between the thinfilm target and the screen when the electrical vector of the laser isparallel to the direction of the electron beam;

FIG. 3 is a plot obtained with the system of FIG. 1 representing therelative intensity (I/ o) of blue light )\=448OA) given off at thenon-luminescent screen as a function of the angle 9 between theelectrical vector of the laser and the direction of the electron beam atdistances r=l5.3 centimeters and r=34.0 centimeters between the thinfilm target and the screen where maxima in accordance with theconditions of FIG. 2 occur; and

FIG. 4 is a diagrammatic representation of a color television tubeincorporating the principles of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The present inventionwill first be described in connection with a basic system which may beused for achieving the interaction phenomenon and then in terms of aparticular embodiment as incorporated in a color television tube. Theterm electromagnetic radiation" as used herein shall refer to energytransmitted through space and through a material medium in the form ofelectromagnetic waves and the term particle shall refer to thoseelementary particles having nonzero rest mass.

The phenomenon can be accomplished using a system such as showndiagrammatically in FIG. 1, wherein an ultra-high vacuum chamber is usedto surround the interaction zone. The chamber comprises a stainlesssteel bell jar l which is evacuated by an ion pump 2, backed up by twosorption pumps 3 and 4. A

liter/sec. Vaclon pump obtainable from Varian Asvelocity beam ofparticles, such as an electron gun 7,

and a means for intercepting the particle beam after passing through thetarget, such as a fluorescent screen 8 or non-luminescent screen 9. Themeans for producing the electromagnetic waves is a laser 10, andoptically flat windows 11 and 12 are provided in the bell jar 1 for thepassage of the laser beam 13. Another optically flat window 14 may beprovided for observing the detector screens 8 and 9.

The target 6, more particularly, is a thin film crystal such as ofsilicon dioxide (SiO- aluminum oxide (A1 or strontium fluoride (SrF Thethickness of the crystal may be of the order of 1,000 Angstroms,depending upon the wavelength of the laser light used, which in thepresent system may be blue light of 4,880 Angstrom wavelength. Thetarget 6 is mounted in the chamber such as by means of a tungsten wiregrid with a portion of the grid supporting about 1 X l millimetersquares of the crystalline film by opposed wires which leave oppositeedges of the film unobstructed to permit the laser beam 13 to shinethrough these edges parallel to the film surface. To avoid any slightimpurities in the film, which might lead to excessive heat absorptionfrom the relatively high intensity laser beam,

the crystalline film should be carefully prepared such as by epitaxialvacuum-deposition in a separate vacuum system of about l0" torr. Thedeposited film may be floated off its substrate under de-ionized waterand caught with the special tungsten wire grid. A small liquid nitrogencooling system 16 can be used to moderate the temperature of the filmsupport during laser irradiation.

The interaction zone, as will be more fully explained, may be providedin various ways, and many different substances and materials will befound suitable, whether amorphous, monocrystalline or polycrystalline,or in the gaseous, liquid or solid state, as long as they possess theproper light-velocity-decreasing properties and dimensio'ns',"a're'transparent to the electromagnetic radiation at the interactingfrequency, and tend to minimize particle scattering.

The irradiating laser beam 13 is directed through the optically flatwindow 11 in"thebelljar 1, passes through the crystalline film target 6and out of the bell jar 1 through the similar window 12 on the oppositeside. Laser optics, such as a suitable system of optical lenses 17 maybe arranged inside the jar adjacent the window 11 to constrict the beamto a diameter of about 10 to 50 micrometers. To study variations in thephenomenon, the laser 10 should be arranged so that the direction of itselectrical vector E may be changed by rotating the laser 10 itself or bymeans of a Pockels cell 18 positioned in the path of the laser beam 13before it enters the bell jar l. A suitable'lase r for use with thissystem is a l0-watt argon ion laser with Brewster angle which produces,as noted previously, a beam of blue light with a wavelength of 4,880Angstroms. However, laser beams of various colors or wavelengths may beused.

The detector screen, as previously noted, may be ofa fluorescent or anon-luminescent material. For observational purposes, interghangeablescreens of each type can be used, which are also adapted to be variablyspaced with respect to the target so that the phenomenon may be fullyobserved. In such a case, an appropriate feed-through screen movementsystem 19 is provided so that, for example, the non-luminescent screen 9can be moved transversely to cover and uncover the fluorescent screen 8during the observation of the phenomenon. The latter screen 8 may be aconventional zinc sulphide fluorescent screen, while the non-luminescentscreen 9 may be of any convenient material, such as quartz or glass, butmany substances will be found suitable, depending upon the particulareffects which are desired to be obtained. A non-luminescent screenconsisting of a polycrystalline smooth alumina disc of 1 inch diameter,such as normally used for microelectronic thin film circuitry, has beenfound to be particularly suitable. The screen movement system mayconsist of magnetic as well as mechanical operators and in addition totransversely displacing screen 9 should also be adapted to vary thedistance between the screens and the target to observe phenomenondependence on this spacing.

The screen side of the target 6 in the present system is covered by athin metal diaphragm 20, such as a sheet of tantalum, which extendsacross the entire cross-section of the chamber and has a small openingor hole of about 50 micrometers diameter at the crystal to permit thepassage of the electron beam 21. This tantalum sheet shields the screens8 and 9 from scattered laser light and any light emitted by the hotcathode of the electron gun 7.

To further shield the screens from the hot cathode of the electron gun7, the crystal target 6 with its grid support 15 may be positioned inthe horizontal orientation and the electron gun 7 then attached to thebell jar l horizontally with a Varian type flange 22 using a coppergasket. Suitable focusing optics 23, such as magnetic and electrostaticlenses and several diaphragms, may be used to shape the beam 21 whichcan then be bent into the vertical direction and passed through threemore small apertures before traversing the thin crystal target 6. Theelectron beam 21 in the present system may be of about 0.5 microampcurrent and a few micrometers diameter and should be accelerated by ahighly stabilized voltage of the order of 50 keV.

For proper operation of this described system, the following procedureshould be followed to maximize the occurrence of the phenomenon. Beforeeach experiment, the electron optics 23 should be adjusted so that theelectron beam 21 passes perpendicularly through an area of thecrystalline film target 6 to provide a good Laue pattern 24 which may beobserved initially on the fluorescent screen 8. The alumina screen 9 maythen be slid into position covering the fluorescent screen 8 completelyand should be cleaned, such as by argon ion bombardment to avoid theoccur rence of a purple fluorescence on the alumina screen 9. It mayalso be necessary to lower the vacuum below 10' torr to overcome thisimpurity problem and completely eliminate the purple fluorescence. Thealumina screen 9 may then be observed through the optical window 14 andwill appear blank with the possible exception of a very weak purplefluorescence at the center spot 25 of the diffraction pattern 24.

When the suitable electron beam 21 has been established, the laser beam13 is turned on and directed to pass through the target 6, in one edgeand out another.

A diffraction pattern whose light spots are of the same color as thelaser light will appear on the nonfluorescent screen 9. It will befurther observed that even though the laser beam 13 intersects theelectron beam 21, if it does not do so while passing through thecrystalline film target 6, the light spots 24 will disappear. Also, thebrightness of the light spots may be varied by varying the direction ofthe electrical vector of the polarized laser light; the spots beingbrightest when the electrical vector lies parallel to the electron beam.The brightness may also be increased by increasing the electron currentor the laser intensity. Removal of the non-luminescent screen 9 resultsin the production of a light pattern on the fluorescent screen whosecolor is a combination of'the color of the laser light and the light ofthe screen phosphors.

The resulting light pattern may be recorded by suitable means outsidethe bell jar l by the positioning of a flat front mirror 26 inside thebell jar 1 at an angle to the screens 8 and 9 and to the observationwindow 14 in the side of the bell jar l. A camera 27a as well as aphotomultiplier tube 27 may be attached to the window 14. A suitablephotomultiplier tube for use with the system described is the RCA type6810A of 14 stages operated from a 2400 volt power supply 28. Using sucha tube, the luminosity of the light spots 24 on the nonfluorescentscreen 9 have been noted to be at least of the order of watt.

To study the phenomenon further, the distance r between the crystallinetarget 6 and the screen 8 and 9 may be varied by means of the screenmovement mechanism 19. To observe any intensity variations, a suitablerecorder 29 is connected to the photomultiplier tube 27 to register theluminosity of the nonfluorescent screen 9, and the motor 30 of therecorder 29 may be slowly driven synchronously with the screen movementmechanism 19. It will be observed that over a range of r=l0 centimetersto r=35 centimeters, a

periodic change of intensity occurs, while the intensity maxima remainsubstantially the same with slight variation. FIG. 2 illustrates asmoothed out copy of a section of such a recording made in the rangefrom r=l0.0 centimeters to r=l 2.5 centimeters. It will be noted thatthe maxima of the curve are essentially equally spaced by a value of Allwhich is equal to 0.85 centimeters, This spacing will also be observedto increase somewhat with an increase of the electron energy, as well aswith an increase in the wavelength of the light.

If the direction of the electric vector E is varied, for example, bymeans of the Pockels cell 18, the maximum intensity of the light spots24 on the non-luminescent screen 9 will occur when the electrical vectorE is in the same direction as the electron beam 21. The intensity willdecrease faster than linearly with the cosine of the angle 0 between thedirection of the electrical vector E and that of the electron beam 21.FIG. 3 illustrates several measurements performed with thephotomultiplier tube 27 mentioned above, at distances of r=l 5.3centimeters and r=34.0 centimeters between the target 6 and the screen9, at which points maxima are observed in a plot in accordance with theconditions in FIG. 2. At these distances, the maxima of the lightintensity I are substantially the same when 0 equals zero, that is whenthe electrical vector E of the light is parallel to the electron beam21, as was noted in FIG. 2. The ordinate of FIG. 3 indicates thefractional level of light intensity I,./I, in relation to these maxima,while the abscissa is the angle 6 between the electron beam 21 and theelectrical vector E of the light. It will be noted that with increasesin the distance r, the peaks of the maximum light intensity becomesharper.

To verify the fact that the phenomenon occurs as a result of theinteraction of the electron beam 21 and the laser light 13, awell-shielded magnet with a field of about 300 gauss may be introducedinto the screen region and the color pattern 24 on the screen will beobserved to be deflected accordingly. Also, when the laser beam 13 isturned off, no light will be observed on the non-luminescent screen,even though the electron beam remains on for a considerable period oftime.

Perhaps a more thorough understanding of the present invention can beachieved if it is considered that the phenomenon may be treated quantummechanically as a single electron process by assuming that the simplewave function,

o)= p[ /fi(p' J)] will be transformed into a superposition of wavefunctions of plane waves separated by the energy fir of the photons,after the electron has passed through the dielectric target.

A closer analysis of the wave function in this form,

I =a IL (E -(uh) a I' (E,,) +a IQ. (E -l'wfi) 2) provides an explanationof the observed periodicity and.

also why the presence of the dielectric target, or some other suitablemeans for creating an interaction zone, will contribute to the producingof the phenomenon. The wave function P in Equation (2) describes thesuperposition of three waves, one represented by unaffected electrons ofenergy E,,; a second represented by electrons of energy E,,+wfi, due toa photon being absorbed; and a third represented by electrons of energyE wfi, due to the emission of a photon. The momentum of an electronwhich absorbs a photon will increase by a value Ap and the momentum ofan electron which emits a photon will decrease by a value Ap Thus, thewave function IQ for electrons with energy E,+mfi is in the form:

and the wave function I. for electrons with energy E;- aili is:

The relationships between the momenta and energy of the different statesare:

(piApL)/2m=E,tmfi (6,7) Thus, Equations l to (4) lead to the wavefunction electron beam so that the dot product signs in Equation (8) maybe neglected.

The Equations (5) to (7) allow the determination of the momentumincrease Ap, and the momentum decrease Ap. by:

Ap =%p(ei%e+---.) (9 where gum/E is the ratio of photon energy toelectron energy and the electron energy is E,, (mv )/2 For the valuesused in the particular system described, 6 is approximately X the photonenergy being 2.54 eV and the electron energy being 5 X 10 eV. Therefore,the series of'Equaltion: (9). can be broken off after the second term.Equation (1 9): indicates that the presence of a third body or somemedium for allowing momentum transfer is in order, since the maximummomentum transfer of a photon to an electron in the direction of theelectron beam without it can only be h'w/c. The conservation of momentumin the electron beam direction can be expressed with Equation (9) by:

2(fiw)/ccos0=p(ei%e (I0) where 0 is again the angle between momentumchange and electron beam direction. Introducingp= mv and F 2 fim/(mvleads to the relationship when e 10'':

V/Ccos0=li%e (it which indicates that the momentum transfer in thedescribed system will not take place in a vacuum, since in vacuum V/C0.41 and the value of /4e l0 Therefore, it will be seen that thephenomenon may be produced using means for creating an interaction zonefulfilling the conditions indicated in Equation (1 I that is, a mediumfor decreasing the speed of light in the zone to approximately that ofthe particle beam velocity. For example, as in the described system, adielectric material can provide the conditions which will satisfy therelationship expressed in Equation l l if placed in a vacuum andsubjected to the electric field inhomogeneities due to the nonuniformityof the laser intensity, which is not an ideally parallel beam, anddiscontinuities at the boundaries between the dielectric and vacuum.

For the determination of the charge density fluctuations, will must beformed and Equation (9) introduced. The real part of 1"? as a functionof space and time will then be:

where A, 0, 11, +a

Equation 12) can be written as A 4a a =4a a and A, a a (I4) In view ofthis, it may be assumed that the probability for increasing the momentumof the electron by Ap while absorbing a photon wfi is almost the same asthe probability for decreasing the momentum of the electron by Ap, whilestimulating emission of a photon mix.

Also it may be assumed that the cross-section for (15) This indicatesthat the phenomenon deals with wave packets whose group velocity is asshould be expected, the electron velocity:

V=(2fim)/(ep) (l6) The amplitude of the wave packets described byEquation l5) varies periodically with the length r of the electron beambetween the thin crystal film target and the screen. The peaks of thevariation along r, as noted from FIG. 2, are separated by equaldistances:

A e being the wavelength of the electron. Using the stated values forL== 5.1 X 10 and p L24 X 10' gr cm sec and Planck's constant 7? L055 X10 erg sec, Equation (17) provides a value of %A= 0.82 cm which issubstantially equal to the distance between two peaks as measured onFIG. 2.

With regard to the coherence of the electromagnetic radiation, althoughcomplete coherence is not required to achieve the interactionphenomenon, still the efficiency of the interaction is significantlyeffected so that a fair degree of coherence is necessary to obtain apractically satisfactory interaction. In view of the present state ofthe art, it would'appear that electromagnetic radiation in the rangefrom the ultraviolet to the infrared and microwave regions could be usedas well as that in the visible spectrum in devices embodying the presentinvention. Similarly, the greatest efficiency is achieved when theelectrical vector of the radiation is polarized in the same direction asthat of particle propagation.

It is also contemplated that particles other than electrons may be usedin the present invention by selecting target media and other means withappropriate parameters to fulfill the relationships and conditons asindicated above.

It will therefore be seen that the interaction of the present inventionmay be accomplished using a variety of particle and electromagneticenergy beams as long as an interaction zone is created which will act tosatisfy the conditions defined in Equation (1 1) for the particularbeams selected.

COLOR TELEVISION TUBE One particular embodiment utilizing the phenomenonof the present invention is its incorporation in a color televisiontube, such as shown diagrammatically in FIG. 4. The tube may beconstructed substantially in the manner of a conventional black andwhite television receiver tube and may compromise a glass housing 40whose interior is evacuated to at least a vacuum level of 10' torr. Theexterior of the tube may be coated with an opaque material, with theexception of the front screen portion 41, which should be lighttransmitting, and the provision of suitable means for permitting passageof the laser beams such as three sets of transparent windows 42, throughwhich the laser light passes into the interior and out of the tube. Acon ventional electron gun 43, arranged at one end of the tube providesthe electron beam 44 which may be focussed by Wehnelt cylinder 45containing a suitable system for varying the beam intensity. A furtherelectron optic system 47 provides for the producing of an appropriatescanning action of the beam 44 over the .display surface or screen 41 ofthe tube.

The modification of the structure in accordance with the presentinvention occurs in the region between the intensity and scanningcontrol means 45 and 47. A thin film target 46 is disposed in the pathof the electron beam 44 and is of an optically transparent dielectricmaterial, such as monocrystalline or polycrystalline, SiO,, M SrTi0,,BaTiO, and the like. As the electron beam 44 will tend to be scatteredin passing through the target 47, a further system of electron opticallenses 48 may be disposed on the screen side of the target to refocusthe beam or, alternatively, a masking diaphragm, such as the tantalumdiaphragm used in the first described system, may be used so that onlythe portion of the beam creating the center spot is used for thescanning operation.

Three lasers, 49, $0 and 51 are appropriately arranged with their beamsdirected respectively through the three sets of transparent windows 42and each passing through the thin film target 46. Of course, the numberof lasers to be used will depend on the color effects which are to beachieved, so that a single frequency modulated laser may suffice, and,as will be seen, the different colors may be blended as desired. In theusual case, three colors will be used so that a helium-neon laser 49 canbe used to produce a red light beam, an

argon laser 50 to produce a green light beam and an argon-ion laser 51to produce a suitable blue light beam.

The intensity of each of the colored beams may be controlled by variousappropriate conventional electronic and electro-optical systems, 52, 53and 54, which are familiar to those skilled in the art. Each beam isfocussed by suitable conventional optical lens systems 55, 56 and 57 topass through the thin film target 47 so as to intersect the electronbeam therein and with the direction of its electrical vector alignedwith the direction of travel of the electron beam. Means should also beprovided for diffusing the three laser beams after passing through thethin film target.

ltwill be appreciated from the preceding analysis of the phenomenon andthe plot in FIG. 2 that the respectivepoints of maximum intensity forthe three different colors will occur at different points along thedistance r and unless a common and constant value for A is establishedfor all three colors, the screen would have to be continuously shiftedin position to obtain a dis play at maximum intensity. Accordingly, itwill be seen from Equation (17) that the following relationship shouldbe established:

A [if/pa. E A= a constant (18) where E is the electron beam voltage inkilovolts and A is the laser light wavelength in Angstroms. To achievethe desired conditions, the DC accelerating voltage may be impressedwith a fast-changing ripple for electron acceleration or three thinfilms may be used, respectively positioned in accordance with therelationship:

where n is an integer and A is a function of the color of the laserlight passing through the film.

In operation, the electron may be scanned in the same manner as the beamin a conventional black-andwhite receiver tube, so that conventionalraster electronics can be used with the electron optics 47. The pictureinformation signal may be fed to the laser intensity control means 52,53 and 54. Thus, the electron beam may be "modulated" in accordance withthe modulation of the three laser beams by the picture signal, so thateach illuminated spot on the display surface of the tube may compriseany one or an appropriate mixture of the three colors.

It will readily be seen by those skilled in the art that this system maybe easily adapted to use as a color cathode ray tube and in otherrelated color display devices. Also, the system may be used for colorcoding and decoding electronic signals in data processing andinformation storage, and in various communications application's.

What is claimed is:

1. Method of creating an interaction between particles andelectromagnetic radiation, comprising the steps'of:

a. directing a beam of particles through an interaction zone;

b. directing a beam of electromagnetic radiation to intersect saidparticle beam in the interaction zone and with its electrical vectorpolarized generally in the direction of said particle beam; and

c. introducing a medium into said interaction zone in the region of beamintersection for allowing momentum transfer among said beams and saidmedium.

2. Method as in claim 1, wherein said electromagnetic radiation beam iscoherent. h

3. Method as in claim 1, wherein said electromagnetic radiation beam isat optical frequencies.

4. Method as in claim 1, wherein the particles of said beam areelectrons.

5. Method as in claim 1, wherein the particles of said beam arepropagating at a given velocity and the speed of light in said medium isapproximately equal to said velocity.

6. Method as in claim 1, wherein said medium is transparent to saidelectromagnetic radiation at the frequency of said radiation.

7. Method as in claim 1, wherein the following relationship isfulfilled:

v/c cos 0= 1 (6/ wherein v is the particle velocity; 0 is the speed oflight in the medium; 5 is the ratio of the energy of the electromagneticradiation to the energy of the particle and is less than 10'; and 0 isthe angle between the change in particle momentum and its originaldirection.

8. Method for producing an electrically controlled color displaycomprising the steps of:

a. directing an electron beam through an optically transparentdielectric target;

b. directing at least one coherent light beam through said targetintersecting said electron beam and with its electric vector lyingsubstantially in the direction of said electron beam;

light beam is varied.

10. Method as in claim 8 wherein the wavelength of said light beam isvaried.

wherein v is the particle velocity; c is the speed of light in themedium; 6 is the ratio of the energy of the electromagnetic radiation tothe energy of the particle and is less than 10; and 6 is the anglebetween the change 5 in particle momentum and its original direction.

18. Apparatus for creating an interaction between particles andelectromagnet radiation comprising:

a. means defining an interaction zone containing a medium for decreasingthe speed of light in the 11. Method of creating an interaction betweena par- Zone below in a Vacuum; ticle beam and a beam of electromagneticradiation, means for Producing a beam of Particles with 3 comprising thesteps of: velocity substantially equal to the speed of light in a.directing the particle beam at a given velocity the Zone q dimming SaidParticle beam through an interaction zone containing a medium 1 through531d med1l" n; for decreasing the speed of light in said zone to i meansf profliufmg Q collefemlelev substantially the velocity of said particlebeam; tromagnetic radiation and directing said radiation and beamthrough said medium to interact with said b. directing theelectromagnetic radiation beam to pamqle beam therein and i electrical fhum-sec Said particle beam in said medium and polarized generally in thedirection of said partlcle beam;and d. means for intersecting saidparticle beam after passing through said zone.

with its electrical vector polarized generally in the direction ofpropagation of said particle beam.

12. Apparatus for creating an interaction between particle andelectromagnetic radiation comprising:

a. means for producing a beam of particles and 2 'directing said beamthrough an interaction zone;

b. means for producing a beam of electromagnetic radiation and directingsaid radiation to intersect said particle beam in the interaction zoneand with its electrical vector polarized generally in the direction ofsaid particle beam; and

c. means in said interaction zone for permitting momentum transferbetween said beams.

13. Apparatus as in claim 12, wherein said means in the interaction zonecomprises a dielectric which is transparent to radiation at thefrequency of said electromagnetic beam.

14. Apparatus as in claim 12, wherein said electromagnetic radiationbeam is coherent and at optical frequencies. 4

15. Apparatus as in claim 12, wherein said particles are electrons.

16. Apparatus as in claim 12, including nonluminescent means forintercepting said particle beam after interaction. 41

17. Apparatus as in claim 12 wherein the respective means are selectedto produce the following relationship:

19. Apparatus for producing an electrically controlled color displaycomprising:

a. an optically transparent dielectric target; b. means for producing anelectron beam and direct- 20. Apparatus as in claim 19 wherein saidcontrolling means is a raster scanning system.

21. Apparatus as in claim 19, wherein said controlling means varies theintensity of the light beam.

22. Apparatus as in claim 19, wherein said controlling means varies thewavelength of the light beam.

23. Apparatus as in claim 19, including non-luminescent means forintercepting said particle beam after passing through said target.

24. Apparatus as in claim 19, including nonfluorescent means forintercepting said particle beam after passing through said target.

25. Apparatus as in claim 19 incorporated in a color television tube.

Patent No. 3 3 9 9 bated May 1, 1973 Inventqflg) Helmut J. Schwarz and\Heinrich W. Hora.

' It is certified that error appears in the above-idntified ptent andthat said Letters Patent are hereby corrected as shown below:

Column '6, equation (3) should read:

1 "Y 5 k 0 mint] 1 equation (4) should read:

B39 3 (E -amt] Column 7', equation (9) should read;

line 6, the term reading "5 x lOeV" Ap 2 p(s i s should read 5 5; 1o

, (cont. on following p I TED STATES mm WNW TMFMATE oi cmiim' WE PatentNo 397309979 Dated May 9 1973 n Helmut J. Schwarz and Heinrich Wo HoraIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

' (comm from page 1) equation (11) should read:

(note "We" shofild read --v/c v I line 25; the expression reading V/c"should read --v/c--='-; v

I equation (12) should read;

2 1 8 r fit A 2a a cos i 2 4 p m 2a c fgr 20mg) MFORM Po-mso (10-69) vUNKTED STATES FATENI'C @FMQE earmwm F eacme Patent No. 3,730,97 I DatedMay 1, 1973 Inve-fitofls) Helmut J. Schwarz and Heinrich Wu. Hora It iscertified that error appears in the above-identified patent I and thatsaid Letters Patent are hereby corrected as shown below:

(con-i;o from page 2) equation (13), that portion of the equationreading A should read ---A I I. I Column 8, equation 16), that portionof the equation reading "V" should read w; I

Column 9, equation (l8) that portion of the equation reading "E w shouldread E 0 Signed and sealed this 25th day of December 1973 r (SEAL)Attest:

EDWARD Mu FLETGHER JRQ RENE Do TEG'Q LEYER Attesting'Officer rActingCommlssioner of Patents new P0-1050 (10-69) I a u scoMM-Dc soa'le-bag Q0 u.'s. GQVIINHINT rnm'rma orrlcl nu o-um-un

1. Method of creating an interaction between particles and electromagnetic radiation, comprising the steps of: a. directing a beam of particles through an interaction zone; b. directing a beam of electromagnetic radiation to intersect said particle beam in the interaction zone and with its electrical vector polarized generally in the direction of said particle beam; and c. introducing a medium into said interaction zone in the region of beam intersection for allowing momentum transfer among said beams and said medium.
 2. Method as in claim 1, wherein said electromagnetic radiation beam is coherent.
 3. Method as in claim 1, wherein said electromagnetic radiation beam is at optical frequencies.
 4. Method as in claim 1, wherein the particles of said beam are electrons.
 5. Method as in claim 1, wherein the particles of said beam are propagating at a given velocity and the speed of light in said medium is approximately equal to said velocity.
 6. Method as in claim 1, wherein said medium is transparent to said electromagnetic radiation at the frequency of said radiation.
 7. Method as in claim 1, wherein the following relationship is fulfilled: v/c cos theta 1 - ( epsilon /4) wherein v is the particle velocity; c is the speed of light in the medium; epsilon is the ratio of the energy of the electromagnetic radiation to the energy of the particle and is less than 10 1; and theta is the angle between the change in particle momentum and its original direction.
 8. Method for producing an electrically controlled color display comprising the steps of: a. directing an electron beam through an optically transparent dielectric target; b. directing at least one coherent light beam through said target intersecting said electron beam and with its electric vector lying substantially in the direction of said electron beam; c. scanning said electron beam after passing through said target in a raster pattern on a display surface; and d. controlling said light beam to vary the light produced on said display surface.
 9. Method as in claim 8 wherein the intensity of said light beam is varied.
 10. Method as in claim 8 wherein the wavelength of said light beam is varied.
 11. Method of creating an interaction between a particle beam and a beam of electromagnetic radiation, comprising the steps of: a. directing the particle beam at a given velocity through an interaction zone containing a medium for decreasing the speed of light in said zone to substantially the velocity of said particle beam; and b. directing the electromagnetic radiation beam to intersect said particle beam in said medium and with its electrical vector polarized generally in the direction of propagation of said particle beam.
 12. Apparatus for creating an interaction between particle and electromagnetic radiation comprising: a. means for producing a beam of particles and directing said beam through an interaction zone; b. means for producing a beam of electromagnetic radiation and directing said radiation to intersect said particle beam in the interaction zone and with its electrical vector polarized generally in the direction of said particle beam; and c. means in said interaction zone for perMitting momentum transfer between said beams.
 13. Apparatus as in claim 12, wherein said means in the interaction zone comprises a dielectric which is transparent to radiation at the frequency of said electromagnetic beam.
 14. Apparatus as in claim 12, wherein said electromagnetic radiation beam is coherent and at optical frequencies.
 15. Apparatus as in claim 12, wherein said particles are electrons.
 16. Apparatus as in claim 12, including nonluminescent means for intercepting said particle beam after interaction.
 17. Apparatus as in claim 12 wherein the respective means are selected to produce the following relationship: v/c cos theta 1 - ( epsilon /4) wherein v is the particle velocity; c is the speed of light in the medium; epsilon is the ratio of the energy of the electromagnetic radiation to the energy of the particle and is less than 10 1; and theta is the angle between the change in particle momentum and its original direction.
 18. Apparatus for creating an interaction between particles and electromagnet radiation comprising: a. means defining an interaction zone containing a medium for decreasing the speed of light in the zone below that in a vacuum; b. means for producing a beam of particles with a velocity substantially equal to the speed of light in the zone and for directing said particle beam through said medium; c. means for producing a beam of coherent electromagnetic radiation and directing said radiation beam through said medium to interact with said particle beam therein and with its electrical vector polarized generally in the direction of said particle beam; and d. means for intersecting said particle beam after passing through said zone.
 19. Apparatus for producing an electrically controlled color display comprising: a. an optically transparent dielectric target; b. means for producing an electron beam and directing said electron beam through said target; c. means for producing a coherent light beam and directing said light beam through said target intersecting said electron beam therein and with its electrical vector polarized generally in the direction of said electron beam; and d. means for controlling the propagation of said electron beam after passing through said target.
 20. Apparatus as in claim 19 wherein said controlling means is a raster scanning system.
 21. Apparatus as in claim 19, wherein said controlling means varies the intensity of the light beam.
 22. Apparatus as in claim 19, wherein said controlling means varies the wavelength of the light beam.
 23. Apparatus as in claim 19, including non-luminescent means for intercepting said particle beam after passing through said target.
 24. Apparatus as in claim 19, including non-fluorescent means for intercepting said particle beam after passing through said target.
 25. Apparatus as in claim 19 incorporated in a color television tube. 